1. Field of the Invention
The present invention relates generally to manipulator welding apparatus and more particularly to control apparatus utilizing a vision correction system for workpiece sensing to operate manipulator welding apparatus to visually detect the deviation between a taught welding path and the actual seam to be welded during a first step and to perform welding along the actual seam of a particular workpiece during a second step.
2. Description of the Prior Art
Various welding apparatus and vision detection systems have been proposed. For example, copending applications Ser. No. 106,039 filed by I. Masaki on Dec. 21, 1979 provides a method and apparatus for detecting any positional deviation of a workpiece from a reference position by means of a visual detection system and an image processor. Further, copending application Ser. No. 066,323 filed by I. Masaki on Aug. 14, 1979 and copending application Ser. No. 077,320 filed by I. Masaki on Sept. 20, 1979 disclose arrangements for interrupting the welding operation and performing the detection of images of the workpiece during the time that the welding is interrupted or the welding current is decreased. Further welding apparatus with control arrangements are disclosed in U.S. Pat. No. 4,115,684 which issued to T. H. Lindbom on Sept. 19, 1978, U.S. Pat. No. 4,086,522 which issued to J. F. Engelberger et al. on Apr. 25, 1978, U.S. Pat. No. 4,030,617 which issued to H. Richter on June 21, 1977, U.S. Pat. No. 4,105,937 which issued to G. Tuda et al. on Aug. 8, 1978 and copending application Ser. No. 154,439 filed by W. Perzley et al. on May 29, 1980.
While the above described arrangements are generally suitable for their intended use, it is difficult to obtain image data of the sensed workpiece during welding. Even in the arrangements where provisions are made to decrease welding current or interrupt welding to obtain images of the workpiece, optical noise in the vision system is still a problem. Further, the vision system is subjected to the welding environment with possible detrimental effects on the vision system. Additionally, if the sensing of the workpiece welding seam is performed during the actual welding of the seam, the vision system carried on the manipulator arm must be positioned near the weld tip. In addition to the vision system being exposed to the welding environment and optical noise resulting therefrom, the weld gun and vision system arrangement may cause clearance problems with obstructions on or around the workpiece and may present various obstacles to the manipulator hand being controlled to move over the welding path. Further, if image data of the workpiece is obtained during the welding operation to provide path correction data, the path computation data must be calculated during the welding process and as the manipulator arm moves over the welding path.